Alternating current clock



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P. M. BLOUGH 2,616,240

Nov. 4, 1952 ALTERNATING CURRENT CLOCK 2 SHEETS-SHEET 2 Original Filed Dec. 2, 1931 a? I f Patented Nov. 4, 1952 ALTERNATING CURRENT CLOCK Paul M. Blough, Chicago, 111., assignor to Joseph A. Kroll, Chicago, Ill.

Substituted for abandoned application Serial No.

578,438, December 2, 1931.

This application December 12, 1951, Serial N0. 261,306

3 Claims.

My invention relates generally to electric clocks and more particularly to clocks adapted to be driven directly by the electric current supplied to consumers for electric light and power service. This application is substituted for applicant's prior abandoned application Serial No. 578,438, filed December 2, 1931, of identical title.

It is now the practice for electric power companies to supply alternating current of accurately regulated frequency for general distribution. While the frequency of the current may vary slightly from minute to minute, the frequency is governed so that the total number of alterna tions per given period, is exactly uniform. A synchronous motor driven clock supplied with current from a source at which the frequency is thus carefully regulated, may be made to indicate the correct time excepting only such slight discrepancies as may result from slight variations in the frequency of the current. equipment and control mechanism, this variation is not cumulative, so that the inaccuracies in time indication by synchronously driven clocks is so small as to be of negligible importance in clocks used for ordinary purposes.

Synchronous motor driven clocks of a type adapted to be used in systems as above described have been known. Synchronous motors of this type consist essentially of a magnetic rotating member which carries salient magnetic poles and which is caused to revolve by the intermittent electro magnetic field of a stationary member positioned near the rotating element. My invention consists of the improvement in clocks of this type to make them more reliable, more simple in construction and less liable to be affected by variations in the current supply.

It is one of the objects of my invention to provide an improved non-self-starting synchronous motor driven time indicating device, which may be easily started either manually or by auxiliary mechanical means, and which, if started at a speed other than the normal synchronous speed, will, as it drops to synchronous speed, automatically get in step and thereafter maintain its exact synchronous speed.

A further object of this invention is to provide an improved synchronous motor having a slow motor speed, whereby the life of the motor will be prolonged and the motor vibration substantially eliminated.

A still further object of this invention is to provide an improved means for mounting the motor parts and gear train upon the clock frame, resulting in a minimum number of parts com- With present patible with compactness and ease of assembly.

A still further object of this invention is to provide an improved manner for mounting the shafts of the clock assembly, whereby all of said shafts will have only a single bearing, with the result that perfect bearing alignment may be had with ease of assembly.

A still further object of this invention is to provide an improved auxiliary mechanical means for launching the motor, whereby the same may be started in the proper direction and at substantially the same speed at all times.

A still further object of this invention is to provide an improved inertia means applicable to the rotor of a synchronous motor, which will be effective in aiding the maintaining of the rotor at synchronous speed.

With the foregoing and other objects in view, which will appear as the description proceeds, the invention consists in certain novel and improved features of construction, arrangement and combination of parts hereinafter more fully described, illustrated in the accompanying drawings, and particularly pointed out in the appended claims, it being understood that various changes in the form, size, shape and minor details of construction may be made Without departing from the spirit or sacrificing any of the advantages of the invention.

For the purpose of facilitating an understanding of my invention, I have illustrated in the accompanying drawing a preferred embodiment thereof, from an inspection of which, when considered in connection with the following description, my invention, its mode of operation, construction and assembly, and many of its advantages should be readily understood and appreciated.

Referring to the drawings in which similar characters of reference are employed to indicate corresponding or similar parts throughout the several figures of the drawings:

Figure 1 is a front elevation of my improved clock, portions of the casing and dial being broken away to show the underlying parts;

Figure 2 is a side elevational View of my improved clock mechanism, the casing therefor being shown in section;

Figure 3 is a vertical sectional View taken on line 3--3 of Figure 1, showing particularly the rotor assembly and the gear train connecting the same with the minute hand shaft; and

Figure 4 is an elevational view taken on line 44 of Figure 2 and looking in a direction of thearrows.

Referring to the-drawings more specifically by 3 characters of reference, the numeral I designates generally a clock casing, which may be of any suitable material and shape for compactly housing my improved clock mechanism. The front of the casing i is provided with the usual crystal 2 of material suitable for that purpose, through which may be readily viewed the dial 3. The clock of this invention comprises the front plate I and the rear plate II, said plates being held in spaced relation by the brass bushing l2, to which the said plates are permanently secured. The clock is driven by a synchronous-motor which comprises a substantially U shaped field frame i3, to the lower portion of which is secured a cross member M. The upperportion of the frame [3 is secured by means of the screws l .to'the rear plate member II. The cross member [4 secured to the frame l3 in any suitable and well known manner, such for example as by means of the screws H5. The coil I1 is wound upon the *cross piece i' hsaid-coil being incircuit with the 'alternatingtcurrent delivered from the commercialpowersource by which the clockis actuated. The uppermost portions of the'upstanding arms of the frame lfiare providedwith a plurality of teeth 5H8, as I shown 'in "Figure 1, said teeth being arranged on an arc of a'circle "so as to match teeth with:a rotor 'l 9, disposedbetween the arms of'tlie-fiel'd frame, as shown in Figure -1 of the drawings and inipositionto be actuated thereby.

The rotor l9 comprises'a magnetic disc "having teeth 2'il, for-med'on its periphery, and is'rigidlysecured to a rotor-"shaftil, which is journaled in the bushin 12, for rotation therein. The rotor shaft is thus mounted i in a single bearing whereby the same may beeasilya'rran'ged in operative position with the assurance that the same will be in proper-alignment at all times. The rotor lfl is of-a'relatively large size-so as to produce a relatively slow speed 7 motor, resulting in a longer life for the motor and in the elimination ofmotor vibrations.

As shown inFigures 2*an'd 3, the rotor-shaft 2 I has mounted" thereon a non-magnetic disc -22; said disc isca'rried onthe shaft'2l, but'is not held against rotationin'relation thereto. One "face of the disc "22 isdisposed'against therotor 'l9, and is provided'with afelt washer 23, which forms a friction facingbetween'thesaid disc and therotor. Theend of the shafti! I hasthreaded thereon a stop or thumbpiece '24, between which and the disc 22 'is'interposed a coil spring 25, whichis'a'daptedfornormally urgin said disc 22 into frictional engagementwith the "rotor l9.

"In response to thefrictional engagement 'of'the rotor l9 and disc '22, the disc normallyrotated substantially in unison with the rotor, although in response to sudden changes in speed'of the rotor I-9 on the shaft 2|theremaybeslipp'age or relative movement, 'whichmovemen't with the "consequent"performance of work and generation of heat and utilization of energy efiect the-regulating function, that is, prevents hunting of the armature and makesthe motor automatically fall into step when launched at a speed other .than the normalsynchronous speed.

The rotor shaft 2| has rigidly mounted thereon at its forward end a disc 2'6,'-upo'n which is eccentrically mounted a. pin-21,'which pin is'a'dapted toengage a ratchet gear 28, which is provided with 60 teeth, "whereby said ratchet gear will make one complete turnin one minute or sixty seconds. A leaf spring 29, secured .to the plate It, 'at 30, is provided for engagin the ratchet gear .28 to. prevent slipping-or over-running-of 'one revolution every 60 minutes.

gear 35, which is alsozp'rovided ontheperiphery thereof with 60 teeth, and will therefore make one revolution in sixty minutes. A leaf spring 36, secured to the plate I0, at 37, is provided for-engagingthe ratchet gear 35 to prevent slippingorover-running of the same.

The; gear 35 is frictionally secured by means of the spring 38 to the minute hand shaft 40, whereby it "will rotate therewith. The shaft 40, as shown injFi'gure3 of the drawings, has a single bearing in a bushing 39, which is rigidly secured to theiplate Ill. The connection between the gear 35 and the shaft 40 may be accomplished by the folowing means: A pinion 4| having a reduced portion is pressed onto the'minute hand shaft 40. The gear 35is loosely mounted-on the said reducedpor-tion-4'2, and a-collar-43 is pressed onto the-free-end of 'the reducediportion E2, the spring 38 being interposed-between the gear 35 and the collar :43. The minute hand is mountedon the free' end of the shaft-4B so as to rotate therewith, and since the, ratchet gear 35 is connected to the shaft 40, said hand 44 .willjmake The shaft '48 has a suitable knurled thumb piece 45-s'ecured at its rearward end by which the clock may be set.

The-pinion 4i carried on the minute hand shaft lflmesheswith' aigear 46, which is rigidly secured to'the'shaft 4'1, having a bearin in a bushing -68, rigidly s'ecured'to the front plate ill]. The

other end of the shaft i 41 has rigidly secured thereto for rotationstherewith a pinion 49, which meshes with .a .gear 50,1-rigidly mounted on a sleeve 5!, which sleeve is loosely mountedon the 'minute hand shaft 40. The sleeve 5i carrie at its forward end the hour hand '52. The hour hand 52 is thus driven by the minute-hand shaft '4 ll, through-the pinion 4 I, gear 46, pinion 4-9 and gear*50,=said gear trainh'aving a reduction ratio of 12'to 1, causing one t'urn of the hour han'd 52 every twelveho'urs.

'The hands Maud-52 register with the dial 3,

through which the Sleeve 5| extends-as shown 'in-the drawings. The said dial may be-supporte'd from the casing I, in which the clock'mechanism is mounted.

The thumb piece 24,-secured-on the rearward end of the-rotor sha'ftil, may be utilized for manually starting the clock,'as a single "twirl of "this thumb piece WiII impart'Sufficient speed to the rotor =19 tocau'se the same to revolve at super synchro-nous speed. *As the rotor slows 'downto synchronous'spee'd dueto the frictional load imposed by the-geantrain'it will fall in' step and continue rotating-at synchronous speed. -A

further and improved mechanism is also provided for starting'the clock. This -mechanism, as shown in Figure 1, comprises a'-plunger :55, the upper end of s which: is. adaptedto extend through thetop wallof'the casing l. The plunge-r55 is slidably mounted 1a suitable bracket :56, which is secured to the frame carrying the clock mechanism. The lower end; of l the; plunger 55 "has rigidly secured thereto a spring steelmem-bert'i, which is disposed inposition to engage the rotor 19 -to impart rotary j movement to the same whenever-the plunger 55 is depressed.

A coil spring 52 is interposed between the bracket 56 and a pin 5:) secured to the plunger, whereby the said coil spring will be efiective for normally holding the plunger in the raised position and out of engagement with the rotor 19. When, however, the plunger 55 is depressed against the action of the coil spring 58, the spring 5? will engage the rotor and move the same in the proper direction, which movement will be sufficient to launch the motor at a speed above synchronism. The provision of my improved starting means will insure the motor being started at all times in the proper direction and at substantially the same speed.

The action of the combination of rotor and frictionally held disc 22 is most effective in practice and may be explained as follows: When the rotor is revolving at any uniform speed or at a speed very nearly uniform, the disc 22 revolves with the rest of the rotor, and there is scarcely any displacement between the disc and rotor. If the speed of the rotor is increased or decreased the inertia of the disc causes it to slip on the shaft and the friction between it and the shaft and rotor constitutes energy dissipation, which work is done at the expense of any force of any kind tending to accelerate or retard the motion of the revolving unit as a whole.

Thus, if the clock is started at a speed greater than the normal synchronous running speed, the natural friction on the bearings and from the load causes it to slow down gradually until the speed of the rotor approaches the normal running speed. When a certain point is reached the rotor will suddenly be violently retarded by the stationary magnetic members, and if it were not for said frictional disc, would be retarded to a point below synchronous speed and would thereafter continue to slow up and eventually stop.

The frictional disc, however, when the sudden retarding action takes place, is retarded at a rate less than the rotating effect on the other portions of the rotor, and will damp the motion of the rotor in such a way as to permit it to continue running in synchronism.

Similarly, the action of the frictional disc is to enable the rotor to fall in step and run synchronously from a speed less than the normal speed.

The rotor carrying the loose disc cannot be made to hunt violently, as hunting or any kind means accelerated motion, which causes work to be done between the disc and the other revolving parts, which clamps the oscillation.

It will be especially noted that the device is designed for a slow motor speed, thus resulting in longer life for the motor and in the elimination of motor vibration. Also, the gear train is extremely simple in construction and is so arranged as to be very compact and to make possible the installation of this mechanism in a small clock. A further feature is the provision of a single bearing for all shaft-s, whereby not only ease of assembly is obtained, but also a perfect bearing alignment.

It is believed that my invention, its mode of construction and assembly, and many of its advantages should be readily understood from the foregoing without further description, and it will be manifest that while a preferred embodiment Of the invention has been shown and described, for illustrative purposes, the structural details are, nevertheless, capable of wide variation within the purview of my invention as defined in the appended claims.

I do not restrict myself in any unessential particulars, but what I claim and desire to secure by Letters Patent is:

1. In an electric motor driven clock, a bushing, a frame comprising a pair of spaced plates connected to each other by said bushing, a motor armature, a shaft bearing said armature journaled in said bushing, a gear train mounted on said frame, said gear train being driven by said armature, and each of the shafts of said gear train having a single bearing which is formed by bushings rigidly secured to one of said plate members.

2. ihe invention of claim 1 further including a stop secured to said shaft in spaced relation to said armature, an inertia member loosely mounted on said shaft between said armature and said stop, a spring compressed between said inertia member and said step and adapted to hold said member against said armature, and a friction facing disposed between said armature and member.

3. The invention of claim 1 further including a driving cam pin secured at one end of said shaft, an inertia member rotatable on said shaft, a coil spring surrounding said shaft, and a stop on the rear end of said shaft, said coil spring being pressed between said armature and stop to hold said inertia member in frictional contact with said armature.

PAUL lVI. BLOUGH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Great Britain Oct. 8, 1947 

